Condition assessment of GFRP-retrofitted concrete cylinders using electromagnetic waves

The objective of this study is to develop an integrated nondestructive testing (NDT) capability, termed FAR NDT (Far-field Airborne Radar NDT), for the detection of defects, damages, and rebars in the near-surface region of glass fiber reinforced polymer (GFRP)-retrofitted concrete cylinders through the use of far-field radar measurements (electromagnetic or EM waves). In this development, two far-field monostatic ISAR (inverse synthetic aperture radar) measurement schemes are identified for collecting radar measurements, and the backprojection algorithm is applied for processing radar measurements into spatial images for visualization and condition assessment. Reconstructed images are further analyzed by mathematical morphology to extract a numerical index representing the feature of the image as a basis for quantitative evaluation. The components of the development include dielectric modeling of materials, laboratory radar measurements, numerical simulation, and image reconstruction. It is found that using the developed technique the presence of near-surface defects can be detected by the oblique incidence measurements. Radar signals in the frequency range of 8 GHz to 18 GHz are found effective for damage detection in the near-surface region of the specimens. Numerical simulation using the finite-difference time-domain (FDTD) method is conducted to understand the propagation and scattering of EM waves from the defects and inclusions in two-dimensional and three-dimensional GFRP-concrete models. The FDTD simulation is capable of predicting the far-field response of GFRP-concrete cylinders and beneficial to better understanding the pattern of field measurements in the application of the FAR NDT technique.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Yu, Tzu-Yang (Tzu-Yang Young), 1973-

Advisor dc:contributor.advisor

• Oral Buyukozturk.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/43749

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/43749